// Source : https://leetcode.com/problems/middle-of-the-linked-list
// Author : Dean Shi
// Date   : 2018-08-10

/***************************************************************************************
 * Given a non-empty, singly linked list with head node head, return a middle node of
 * linked list.
 *
 * If there are two middle nodes, return the second middle node.
 *
 * Example 1:
 *
 * Input: [1,2,3,4,5]
 * Output: Node 3 from this list (Serialization: [3,4,5])
 * The returned node has value 3.  (The judge's serialization of this node is [3,4,5]).
 * Note that we returned a ListNode object ans, such that:
 * ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.
 *
 * Example 2:
 *
 * Input: [1,2,3,4,5,6]
 * Output: Node 4 from this list (Serialization: [4,5,6])
 * Since the list has two middle nodes with values 3 and 4, we return the second one.
 *
 * Note:
 *
 * The number of nodes in the given list will be between 1 and 100.
 *
 ***************************************************************************************/

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var middleNode = function(head) {
    let fastPt = head
    let slowPt = head

    while (fastPt && fastPt.next) {
        fastPt = fastPt.next.next
        slowPt = slowPt.next
    }
    return slowPt
};
